The Illinois Farm Sustainability Calculator is a spreadsheet-based model capable of quantifying and analyzing some of the most important measures of agricultural sustainability for any farm in the state of Illinois. Users input data from their farm including soil information, the production area of each crop, nutrients added to the fields, tillage methods, the number and type of animals raised, livestock dietary requirements, energy sources used, building energy use, product hauling distances etc. The model takes these inputs, combines them with data concerning crop productivity, carbon sequestration and emissions, energy use for different types of tillage and buildings, alternative energy production, and many other subjects. From these parameters, IFSC produces final balance sheets for animal feed production vs. consumption, energy production vs. consumption, carbon sequestration vs. carbon emission, and nitrate runoff. It also indicates how many people the farm can feed. In other words, IFSC allows its user to discover whether or not their current farm design is sustainable and test it against any number of hypothetical farm designs until a sustainable design is reached. Development of the IFSC was funded by the Dudley Smith Initiative.